Tests using entity fields of the field field type.
public function testTestItem() {
// Verify entity creation.
$entity = entity_create('entity_test', array());
$value = rand(1, 10);
$entity->field_test = $value;
$entity->name->value = $this
->randomName();
$entity
->save();
// Verify entity has been created properly.
$id = $entity
->id();
$entity = entity_load('entity_test', $id);
$this
->assertTrue($entity->field_test instanceof FieldInterface, 'Field implements interface.');
$this
->assertTrue($entity->field_test[0] instanceof FieldItemInterface, 'Field item implements interface.');
$this
->assertEqual($entity->field_test->value, $value);
$this
->assertEqual($entity->field_test[0]->value, $value);
// Verify changing the field value.
$new_value = rand(1, 10);
$entity->field_test->value = $new_value;
$this
->assertEqual($entity->field_test->value, $new_value);
// Read changed entity and assert changed values.
$entity
->save();
$entity = entity_load('entity_test', $id);
$this
->assertEqual($entity->field_test->value, $new_value);
}